A flexographic printing press, which is installed on, for example, a manufacturing line of corrugated board boxes, carries out printing by supplying an ink in an ink chamber formed along the longitudinal axis direction of an anilox roll into the cells on the outer circumference face of the anilox roll and further transferring the ink on the anilox roll to a printing plate. The ink in the ink chamber circulates by being supplied from an ink can through a supplying pipe and returning to the ink can through a returning pipe.
In changing of an ink of such a flexographic printing press, recovering the ink, washing the ink circulating path, and circulating the next ink are required. It is important to accomplish this changing procedure in a shorter time to enhance the working efficiency of the printing press. In particular, the art has a problem of shortening the time that washing takes by efficiently washing inside the ink circulating path. Since an ink used for a flexographic printing is usually water-base ink, it is possible to use water to wash the ink circulating path.
In order to solve the above problem, Patent Literature 1 discloses a technique of flowing a the mixture of the washing water and air at a high velocity by mixing compressed air into the circulating path when the washing water is circulating the ink circulating path. This can enhance the washing efficiency of the inside of the ink chamber by an agitating action and a turbulent flow forming action of the washing water by bubbles and an energy of high-velocity flow of the washing water.
Here, an ink chamber is defined as a space enclosed by a chamber frame arranged opposite to the outer circumference face of an anilox roll, a seal blade installed at the top end of the chamber frame, a doctor blade installed at the bottom end of the chamber frame, the anilox roll that rotates in contact with these blades, and side plates. The outer circumference face of the anilox roll rotates in the direction of from the seal blade to the doctor blade. An ink in the ink chamber is applied to the outer circumference of the anilox roll in the range between these blades, and the surplus ink thereon is scraped off by the doctor blade.
When the outer circumference face of the anilox roll enters the seal blade, an ink remaining on the outer circumference face of the anilox roll adheres to the upper surface side of the seal blade, and the adhering ink gradually gathers in the V-shaped space formed between the upper surface of the seal blade and the outer circumference face (sic) of the anilox roll. If the ink on the upper surface of the seal blade is not removed when the ink is to be changed, the ink after the changing is to be contaminated with the left ink. Besides, if the ink on the upper surface of the seal blade is not removed when the printing press is being washed, the left ink adheres to the anilox roll again to clog the cells. For the above, the left ink on the upper surface needs to be washed off when the printing press is being washed.
Above the seal blade, a pipe to supply dampening water to the outer circumference face of the anilox roll is arranged. The dampening water is used to adjust the ink concentration, avoid fixation of the ink to the side plates, and prevent the ink from sticking to the cells on the surface of the anilox roll being gradually dried as the ink in the ink chamber reduces when the ink is changed to another ink and from consequent clogging the cells. The technique disclosed in Patent Literature 1 supplies the dampening water from the pipe to the anilox roll when washing the printing press, which means the dampening water functions as washing water capable of washing off the ink adhered to the upper surface side of the seal blade.